poj 1611

並查集入門

一個社團的合併一次，最後統計和0是在相同集合的人

#include<iostream>
#include<cstdio>
#include<algorithm>
using namespace std;
const int maxn = 30000 + 10;
int p[maxn];
int a[maxn];
int tofind(int x){
    if(x == p[x]) return x;
    return p[x] = tofind(p[x]);
}
void join(int x, int y){
    int px = tofind(x);
    int py = tofind(y);
    p[px] = p[y];
}
int main(){
    int n, m, k;
    while(scanf("%d%d", &n, &m), n + m){
        for(int i = 0; i <= n; i++) p[i] = i;
        for(int j = 0; j < m; j++){
            scanf("%d", &k);
            for(int i = 0; i < k; i++){
                scanf("%d", &a[i]);
                if(i){
                    if(tofind(a[i-1]) != tofind(a[i])){
                        join(a[i-1], a[i]);
                    }
                }
            }
        }
        int ff = tofind(0);
        int ans = 1;
        for(int i = 1; i <= n; i++){
            if(tofind(i) == ff) ans++;
        }
        printf("%d\n", ans);
    }
    return 0;
}